The invention relates to a reciprocating internal combustion engine.
In particular, the invention concerns such an engine which is of the kind comprising: a cylinder having a substantially horizontal axis and having one end thereof shaped as a combustion chamber and the other end thereof opening into a crankcase adapted to receive a lubricating atmosphere, said cylinder having a bottom zone where liquid lubricant may collect when the engine is stationary; a piston slidable in said cylinder and having a space therein communicating with said crankcase, said piston having an outside surface formed with at least one peripheral sealing groove and a peripheral scraper groove, said peripheral grooves being of rectangular cross-section with a base and a pair of transverse surfaces, said scraper groove being nearest said other end of said cylinder and having the base thereof formed with orifices via which said scraper groove communicates with said space in said piston; a substantially rectangular cross-section piston ring received in each said sealing groove; and a substantially rectangular cross-section scraper ring received in said scraper groove; said piston being received in said cylinder with clearance whereby annular gaps are formed between said outside surface of said piston and said cylinder on each side of each of said piston and scraper rings.
Internal combustion engines of such a kind in which the cylinders have their axes extending substantially horizontally are usually referred to as flat cylinder engines.
The invention relates more particularly, as being the case where the invention seems likely to be most useful, but not exclusively, to internal combustion engines having cylinders whose cylindrical peripheral wall is completely closed and which operate on a four-stroke cycle.
It has been found that flat cylinder engines of this kind often produce more exhaust smoke on starting than is produced by engines having other cylinder arrangements.